NFS: create common nfs_pgio_header for both read and write

In order to avoid duplicating all the data in nfs_read_data whenever we
split it up into multiple RPC calls (either due to a short read result
or due to rsize < PAGE_SIZE), we split out the bits that are the same
per RPC call into a separate "header" structure.

The goal this patch moves towards is to have a single header
refcounted by several rpc_data structures.  Thus, want to always refer
from rpc_data to the header, and not the other way.  This patch comes
close to that ideal, but the directio code currently needs some
special casing, isolated in the nfs_direct_[read_write]hdr_release()
functions.  This will be dealt with in a future patch.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 650127fd24bb..7dc9be1a6e1a 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -296,6 +296,8 @@ extern int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh);
 
 struct nfs_pageio_descriptor;
 /* read.c */
+extern struct nfs_read_header *nfs_readhdr_alloc(unsigned int npages);
+extern void nfs_readhdr_free(struct nfs_pgio_header *hdr);
 extern int nfs_initiate_read(struct rpc_clnt *clnt,
                              struct nfs_read_data *data,
                              const struct rpc_call_ops *call_ops);
@@ -309,6 +311,8 @@ extern void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio);
 extern void nfs_readdata_release(struct nfs_read_data *rdata);
 
 /* write.c */
+extern struct nfs_write_header *nfs_writehdr_alloc(unsigned int npages);
+extern void nfs_writehdr_free(struct nfs_pgio_header *hdr);
 extern int nfs_generic_flush(struct nfs_pageio_descriptor *desc,
                 struct list_head *head);
 extern void nfs_pageio_init_write_mds(struct nfs_pageio_descriptor *pgio,